Ablation devices with sensor structures

ABSTRACT

A cardiac ablation device, including a steerable catheter ( 10 ) and an expandable ablation element ( 18 ) incorporating one or more balloons ( 20, 22 ) at the distal end of the catheter, has a continuous passageway ( 28, 30 ) extending through it from the proximal end of the catheter to the distal side of the expandable ablation element. A probe ( 72 ) carrying electrodes is introduced through this passageway and deploys, under the influence of its own resilience, to a structure incorporating a loop ( 82 ) which is automatically aligned with the axis of the expandable ablation device, so that minimal manipulation is required to place the sensor probe.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing date of U.S.Provisional Patent Application No. 60/563,581, filed Apr. 19, 2004, thedisclosure of which is hereby incorporated herein by reference.

BACKGROUND ART

The present invention relates to apparatus and methods for cardiacablation and to sensor structures useful in such apparatus and methods.

Contraction or “beating” of the heart is controlled by electricalimpulses generated at nodes within the heart and transmitted alongconductive pathways extending within the wall of the heart. Certaindiseases of the heart known as cardiac arrhythmias involve abnormalgeneration or conduction of the electrical impulses. One such arrhythmiais atrial fibrillation or “AF.” Certain cardiac arrhythmias can betreated by deliberately damaging the tissue along a path crossing aroute of abnormal conduction, either by surgically cutting the tissue orby applying energy or chemicals to the tissue, so as to form scar. Thescar blocks the abnormal conduction. For example, in treatment of AF, ithas been proposed to ablate tissue in a partial or complete loop arounda pulmonary vein within the vein itself, within the ostium or openingconnecting the vein to the heart, or within the wall of the heartsurrounding the ostium. It would be desirable to perform such ablationusing a catheter-based device which can be advanced into the heartthrough the patient's circulatory system.

As described in co-pending, commonly assigned U.S. Pat. No. 6,635,054,the disclosure of which is incorporated by reference herein, anexpansible structure is used as a reflector for directing and focusingultrasonic waves from an ultrasonic transducer into a region of tissueto be ablated. As further described in the '054 patent, certainpreferred embodiments according to that disclosure include an expansiblestructure incorporating a structural balloon which is inflated with aliquid and a reflector balloon inflated with a gas. The balloons share acommon wall. The balloons are configured so that the common wall has agenerally parabolic shape. Because the liquid in the structural balloonand the gas in the reflector balloon have substantially differentacoustic impedances, the interface between the balloons at the commonwall is a nearly perfect reflector for ultrasonic waves. Ultrasonicwaves are emitted from a small transducer within the structural balloonand passes radially outwardly from the emitter to the reflector. Thereflector redirects the ultrasonic waves and focuses it into a ring-likeablation region encircling the central axis of the emitter and balloons.This ablation region is just forward of the structural balloon. Thus,the ultrasonic waves will ablate tissue in a region encircling thecentral axis or forward-to-rearward axis of the balloon structure.

This arrangement can be used, for example, to treat atrial fibrillationby ablating a circular region of myocardial tissue encircling the ostiumof a pulmonary vein. The ablated tissue forms a barrier to abnormalelectrical impulses which can be transmitted along the pulmonary veinsand, thus, isolates the myocardial tissue of the atrium from theabnormal impulses. To provide effective treatment in this mode ofoperation, the ring-like focal region should encircle the ostium andshould lie in a plane which is parallel or nearly parallel with theinner surface of the heart. In some embodiments disclosed in the '054patent, the structural balloon is provided with a forwardly projectingtip at its central or forward-to-rearward axis.

As disclosed in commonly assigned U.S. Provisional Patent ApplicationSer. No. 60/448,804, filed Feb. 20, 2003, and in commonly assigned,co-pending U.S. Published Patent Application No. 2004/0176757(hereinafter “the '757 application”) and PCT International ApplicationNo. PCT/US04/05197, the disclosures of which are incorporated byreference herein, a catheter-carried expansible ablation structure asdisclosed in the '054 patent can be equipped with a steering mechanismso that the orientation of the expansible structure relative to theheart can be controlled by the physician without relying upon physicalengagement with the pulmonary vein or pulmonary vein ostium. This allowsthe apparatus to be positioned with the loop-like region lying in aplane substantially parallel to the heart wall in the region to beablated, regardless of the orientation of the pulmonary veins relativeto the heart wall and regardless of the exact anatomy of the pulmonaryvein ostium in the particular patient to be treated.

As also disclosed in the '757 application, the catheter and theexpansible structure desirably define a continuous passageway extendingfrom the proximal end of the catheter to the distal or forward side ofthe expansible structure, and communicating with a port open on thedistal side of the expansible structure. A contrast medium can beinjected through this port while the device is in its expandedcondition. This allows the physician to obtain an image of theexpansible structure along with the heart and pulmonary veins before orduring application of ultrasonic energy, so as to confirm properplacement of the device to form a lesion in the desired location.Further, the steering arrangement allows the physician to reposition thedevice so as to form multiple lesions. The lesions formed may includeboth loop-like lesions surrounding a pulmonary vein ostium andsubstantially linear lesions formed by placing the plane of theloop-like ablation region at a substantial angle to the plane of theheart wall, so that ablation occurs only along a small sector of theloop-like ablation region.

It is often desirable to monitor electrical signals propagating withinthe heart. For example, McGee et al., U.S. Pat. No. 5,860,920, disclosesa structure incorporating an elongated element with numerous electrodesdisposed along a distal region of the structure. The structure isadvanced into the heart within a guide tube or sheath, which is thenretracted so as to expose the distal region. In this condition, thedistal region, under its own resilience, forms itself into a hoop shape,which can be pressed into engagement with a region of the heart wall as,for example, a region surrounding the bicuspid valve or the mitralvalve. The electrodes pick up electrical signals propagating within theheart. The electrodes can be connected to a source of electrical energy,so that the electrical energy applied through the electrodes ablates thecardiac tissue. Swanson et al., U.S. Pat. No. 5,582,609, disclosesanother loop-forming structure carrying electrodes for electricalablation. Fuimaono et al., U.S. Pat. No. 6,628,976, discloses a catheterwith a similar loop-like structure said to be useful in mappingelectrical activity or “wavelets” within a pulmonary vein, coronarysinus or other “tubular structure” prior to treatment of the condition.

Marcus et al., U.S. Pat. No. 5,295,484, discloses a catheter carryingboth an ultrasonic transducer and electrodes for sensing electricalpotentials within the heart. These electrodes can be used to allow thephysician to determine whether the arrhythmia has persisted after theablation process. Also, the aforementioned '054 patent and '054 patentdisclose, in certain embodiments, expansible balloon structures havingring-like electrodes thereon for detecting electrical signals within theheart.

Despite all of these efforts in the art, however, still furtherimprovement would be desirable. Providing electrical sensing structureson a balloon-like or other expansible ablation device complicatesfabrication of the device and makes it more difficult to make the devicecollapse to a small diameter for advancing or withdrawing the devicethrough the vascular system. Further, mounting the electrodes on thesame catheter as an ultrasonic transducer, as disclosed in the '484patent, limits placement of the electrodes and the configuration of thetransducer array and associated structures. The particular structuresshown in the '484 patent, for example, are not well suited to formationof a ring-like lesion or sensing of electrical potentials at numerouslocations. Use of a loop-forming sensing element entirely divorced froman ablation device, as contemplated in U.S. Pat. No. 6,628,976,necessarily requires separate steps for placement of such a device whichadds both complexity and risk to the procedure.

SUMMARY OF THE INVENTION

One aspect of the present invention provides apparatus for cardiactreatment which includes a catheter having proximal and distal ends anda lumen, as well as an expansible ablation device mounted at or near thedistal end of the catheter. The ablation device has a collapsedcondition and an expanded condition, and is operative to apply energy tocardiac tissues in proximity to the device when the device is in theexpanded condition. In its expanded condition, the device and catheterdefine a port open to the exterior of the expansible ablation device onthe distal side of the device. Desirably, the ablation device defines abore extending through the ablation device. The bore has a first endcommunicating with the lumen and a second end defining the port.

Apparatus according to this aspect of the invention desirably alsoincludes an elongated sensor probe which also has proximal and distalends. The sensor probe includes one or more electrodes disposed adjacentthe distal end of the sensor probe. The lumen and the ablation deviceare constructed and arranged so that the sensor probe can be removablypositioned in the passageway, with the distal end of the sensor probeprojecting out of the ablation device through the port.

The ablation device may be arranged to direct energy into a loop-likeablation region which encircles the port. Most preferably, theexpansible ablation device includes an ultrasonic emitter and anexpansible energy-directing structure, such as a balloon structure,adapted to direct ultrasonic energy from the emitter into the loop-likeregion when the expansible ablation device is in its expanded condition.

The expansible inflation device desirably defines a forward-to-rearwardaxis, and the loop-like ablation region has an axis substantiallycoaxial with this forward-to-rearward axis. Desirably, the port isdisposed on or adjacent to the forward-to-rearward axis of the ablationdevice, and the sensor probe includes a distal region carrying theelectrode or electrodes. The distal region projects from the port whenthe sensor probe is positioned in the lumen of the catheter and the boreof the ablation device. Desirably, the sensor probe is constructed andarranged so that the distal region tends to form a hoop when the distalregion projects from the port. The hoop desirably encircles theforward-to-rearward axis, and may be substantially coaxial with theforward-to-rearward axis and with the loop-like ablation region.

As further discussed below, apparatus according to this aspect of theinvention allows the physician to position the expansible ablationstructure as desired as, for example, to form a ring-like lesion.However, once the ablation device has been positioned, the sensor probecan be introduced readily through the passageway and is automaticallyaligned with the area to be ablated. For example, where the apparatus isused to form a ring-like lesion around a pulmonary vein or pulmonaryvein ostium, the sensor probe will automatically be placed in alignmentwith the lesion and in alignment with the pulmonary vein and pulmonaryvein ostium when it is introduced through the lumen and bore. Dependingupon the radius of the hoop formed by the sensor, the hoop may bedisposed inside the lesion to monitor electrical activity within thearea enclosed or to be enclosed by the lesion. Alternatively, where theradius of the hoop formed by the sensing probe exceeds the radius of theablation region, the hoop will lie outside of the ablation region, andwill monitor electrical activity in this region.

The removable sensor probe does not impede other procedures such asintroduction of a contrast medium through the passageway duringpositioning. The sensor probe can be placed at any time during theprocedure to monitor electrical activity before or after ablation, oreven during ablation. Because the catheter and ablation device serve asan introducer structure for the sensor probe, the sensor probe can beintroduced readily, without interrupting the procedure. Moreover,because the sensor probe is removable, the apparatus may include morethan one sensor probe, which may have different configurations anddifferent sizes, so that the sensing electrodes can be placed atdifferent locations.

A further aspect of the invention provides methods of cardiac ablationwhich include the steps of advancing an apparatus including a catheterand an expansible ablation device into the subject while the ablationdevice is in a collapsed condition, until the ablation device isdisposed in a chamber of the subject heart, and then expanding theablation device to an expanded condition. In a method according to thisaspect of the invention, the ablation device desirably is positioned ina desired disposition relative to the heart and actuated to apply energyin a loop-like region having a predetermined spatial relationship to theablation device, and thereby ablate the tissue in this region so as toform a lesion. Methods according to the invention desirably furtherinclude the step of advancing a sensing probe through a continuouspassageway from the proximal end of the catheter through the ablationdevice, so that a distal region of the sensing probe projects out of aport on the ablation device and contacts tissue of the subject adjacentthe ablation device. In methods according to this aspect of theinvention, the ablation device desirably at least partially positionsthe projecting distal region of the sensing probe relative to the heart.The method desirably further includes the step of detecting electricalsignals in the subject using the sensing probe. Methods according tothis aspect of the invention afford advantages similar to thosediscussed above in connection with the apparatus.

Yet another aspect of the invention provides a probe which includes aprobe body having an undeployed condition and a deployed condition, andone or more functional elements such as electrodes carried on the probebody. The probe body, in its undeployed condition, desirably iselongated and flexible, and desirably includes a distal region carryingthe functional elements. In its deployed condition, the probe bodyincludes a base portion extending in a distal direction, and a limbextending from the distal end of the base portion in a radial directiontransverse to the distal direction. The limb also extends in a proximaldirection opposite to the distal direction. The limb has an outer endremote from the base portion. In the deployed condition, the probe bodydesirably also forms a hoop extending from the outer end of the limb, atleast partially around the base portion. The hoop desirably carries oneor more of the functional elements.

A probe according to this aspect of the invention desirably is used incombination with an introducer structure having proximal and distal endsand a port adjacent the distal end of the introducer structure, as wellas a passageway extending from adjacent the proximal end to the port.The probe body in its undeployed condition desirably is slideable in thepassageway. In the deployed condition, the base portion of the probebody extends in the passageway and projects from the port. Theintroducer structure may include a catheter and an expansible ablationdevice as discussed above. The ablation device, in its expandedcondition, may define a distal wall, and the port may be disposed on orforward of the distal wall. The ablation device may have a projectionextending forwardly from the distal wall when the ablation device is inthe expanded condition, and the port may be disposed on this projection.When the sensor probe is in its deployed condition, the base portionprojects out of the port forward of the distal wall, whereas the limbportion extends rearwardly towards the distal wall, and the hoop regionoverlies the distal wall and extends around the projection. Statedanother way, in the deployed condition, the sensor probe extends out ofthe port and rearwardly towards the distal wall, so as to place the hoopregion in proximity to or abutting the distal wall of the ablationdevice. Desirably, the probe body is a self-deploying resilientstructure which is arranged to form the configuration including the limband hoop region spontaneously, under the influence of its ownresilience, as the distal end of the probe body is advanced outwardlythrough the port.

These and other objects, features and advantages of the presentinvention will be more readily apparent from the detailed description ofthe preferred embodiments set forth below, taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic, partial sectional view of apparatus inaccordance with one embodiment of the invention during one stage of amethod in accordance with an embodiment of the invention.

FIG. 2 is a fragmentary, diagrammatic perspective view depictingcomponents of the apparatus shown in FIG. 1 at another stage in themethod.

FIG. 3 is a diagrammatic sectional view taken along line 3-3 in FIG. 2.

FIG. 4 is a diagrammatic perspective view of the components illustratedin FIG. 2 during another stage in the method.

FIG. 5 is a fragmentary, diagrammatic elevational view depicting aportion of apparatus in accordance with another embodiment of theinvention.

FIG. 6 is a diagrammatic perspective view depicting a component of theapparatus shown in FIG. 5.

FIGS. 7-14 are schematic perspective views depicting portions of theapparatus shown in FIGS. 5 and 6 during successive stages of operation.

FIG. 15 is a diagrammatic elevational view of a probe in accordance witha further embodiment of the invention.

FIG. 16 is a fragmentary diagrammatic sectional view depicting a portionof the probe shown in FIG. 15.

FIG. 17 is a fragmentary diagrammatic sectional view depicting a furtherportion of the probe shown in FIG. 15.

FIG. 18 is a diagrammatic perspective view depicting a portion of theprobe shown in FIG. 15.

BEST MODE FOR CARRYING OUT INVENTION

As seen in FIG. 1, apparatus according to one embodiment of theinvention includes an insertable structure 10 incorporating an elongatedcatheter 12 having a proximal end 14, which remains outside of the body,and a distal end 16 adapted for insertion into the body of the subject.As used in this disclosure with reference to structures which areadvanced into the body of a subject, the “distal” end of such astructure should be taken as the end which is inserted first into thebody and which penetrates to the greatest depth within the body, whereasthe proximal end is the end of the structure opposite to the distal end.The insertable structure 10 also includes an ablation unit 18 mounted tothe catheter adjacent distal end 16. Ablation unit 18 incorporates areflector balloon 20 and a structural balloon 22 having a common wall24. Reflector balloon 20 is linked to an inflation lumen (not shown) incatheter 10, which extends to the proximal end of the catheter and whichis connected, during use, to a source of a gas under pressure, such asair or, more preferably, carbon dioxide, as, for example, to agas-filled hypodermic syringe, so that the reflector balloon can beinflated with a gas. Structural balloon 22 is connected through aseparate inflation lumen (not shown) to a source of a liquid such asisotonic saline solution, so that structural balloon 22 can be inflatedwith the liquid. A cylindrical ultrasonic emitter 23 is mounted withinthe structural balloon. Balloons 20 and 22, and particularly the commonwall 24 separating the balloons, are designed so that in their inflated,operative condition illustrated in FIG. 1, the balloons are in the formof bodies of revolution about a central or forward-to-rearward axis 26.Emitter 23 is cylindrical and is coaxial with the balloons.

A tube defining a bore 28 extends through the structural balloon at thecentral axis 26. Tube bore 28 communicates with a port 29 on or forwardof the forward wall 38 of the structural balloon. Tube bore 28 alsocommunicates with a lumen 30 within catheter 12. Lumen 30 extends to theproximal end 14 of the catheter and is provided with a suitable fluidconnection such as a Luer hub. Tube bore 28 and lumen 30 together form acontinuous passageway extending from the outlet port 29, just distal tothe ablation device back to the proximal end 14 of the catheter. Asfurther described in co-pending, commonly assigned U.S. patentapplication Ser. No. 10/244,271, filed Sep. 16, 2002, now U.S. Pat. No.6,808,524 (“the '524 patent”), the disclosure of which is incorporatedby reference herein, tube 28 may be formed from a material such as anexpanded polymer of the type commonly used in vascular grafts, so thatthe interior bore of the tube remains patent when the tube is stretched.

As also disclosed in the '524 patent, a coil spring 34 may be providedwithin the structural balloon, such that the coil spring surrounds tube28. A reinforcing structure which may include one or more rigid tubes ofmetal or a rigid polymer such as polyether ether ketone (“PEEK”) 36extends coaxially with the tube defining bore 28 and spring 34. In theparticular embodiment shown in FIG. 1, the rigid tubular structure 36 isdisposed outside of tube spring 34; in other embodiments, the rigid tubeor tubes can be disposed within spring 34, inside or outside of tube 28,so that the rigid tube or tubes define a portion of the bore. Asdescribed in greater detail in the '524 patent and in the aforementioned'757 application, the spring is compressed when the balloons are in theinflated, expanded state. When the balloons are deflated, the springexpands and moves the forward wall 38 of the structural balloon in theforward or distal direction F (up and to the left, as seen in FIG. 1)relative to the rearward or proximal end of the balloon and relative tothe catheter 12, thereby collapsing the balloon in a radial direction,and also twists the balloons about axis 26 to facilitate radial collapseand formation of a small, radially compact unit for withdrawal from thepatient. However, when the balloons are inflated, the spring iscompressed and reinforcing element 36 engages a rigid mounting 40attached to the distal end 16 of the catheter, which mounting also holdsultrasonic emitter 23. This assures that the axis 26 of the balloonstructure is precisely aligned with the axis of the emitter andreinforces the balloon against deflection transverse to the axis 26.

In the arrangement depicted in FIG. 1, the tubular reinforcing element36 abuts the distal end of the mounting 40. In a variant, the mountingis telescopically received within the tubular reinforcing element. Thus,as the balloons are inflated, the tubular reinforcing element 36 movesproximally or rearwardly so that the distal end of the mounting 40enters into the tubular reinforcing element before the balloons arefully inflated. In the fully-inflated condition, the tubular reinforcingelement remains slightly distal or forward of the transducer 23 or elseabuts the distal end of the transducer. Engagement between the mountingand the reinforcing element helps prevent kinking or displacement of thestructure transverse to axis 26 when the structure is in apartially-inflated or fully-inflated condition.

The common wall 24 separating the balloons forms an active, reflectiveinterface. This active interface desirably has the form of a surface ofrevolution of a parabolic section around the central axis 26. When theballoons are in their inflated, expanded configuration shown in FIG. 1,ultrasonic waves emitted by emitter 23 are directed radially outwardlyaway from axis 26 and impinge on the parabolic active interface 24,where it is reflected forwardly and slightly outwardly away from axis 26and focused so that the ultrasonic waves emitted along various pathsmutually reinforces within a ring-like ablation region A, just forwardof the forward wall 38 of the structural balloon encircling axis 26. Thefocused ultrasonic waves in this region can effectively ablatemyocardial tissue and form a substantial conduction block extendingthrough the heart wall in a relatively short time, typically about aminute or less.

Catheter 10 includes a bendable section 60. A steering mechanism isprovided for selectively bending section 60 so as to orient the ablationdevice 18 and the forward-to-rearward axis 26 of the ablation device. Inthe particular embodiment depicted, the steering mechanism includes apull wire 62 extending through a lumen 64, a portion of which is shownin FIG. 1. The pull-wire has a distal end 66 affixed to the distal end16 of the catheter, or to the ablation device itself. The proximal end68 of the pull wire is connected to a handle or other appropriate devicefor manipulating the pull wire relative to the catheter. Oneparticularly useful arrangement of the pull wire is further described inthe aforementioned '757 application. By manipulating the pull wire, thebendable section 60 can be bent to a greater degree, or can be allowedto straighten. Also, the catheter structure desirably is “torqueable,”so that rotation applied to the catheter structure about its own axis atthe proximal end is transmitted through the catheter to the distal end.Thus, the bendable section 60 can be rotated so as to change theorientation of the bendable section and, thus, the orientation of axis26. The pull wire arrangement is merely exemplary of the numerousstructures which can be used to provide steerability to the catheter.

The apparatus further includes an elongated sensor probe 72 having aproximal end 74 and a distal end 76. The probe includes an elongatedresilient body 78 having a diameter smaller than the inside diameter oflumen 30. A plurality of electrodes 80 (FIGS. 2 and 4) extend around theprobe body in an operative region 82 adjacent the distal end of theprobe, also referred to as a “hoop region.” The probe body also includesa juncture region 84 disposed proximal to the operative region and amain or base region 86 extending from the juncture region to theproximal end 74 of the probe. A connector 88 is provided at the proximalend of the probe. As best seen in FIG. 3, the probe body 78 includes adielectric layer 90 and conductors 92 extending within the dielectriclayer from electrodes 80 to connector 88 (FIG. 2). The probe body alsoincludes a resilient metallic element 94 extending along the length ofthe probe body. Element 94 may be a super elastic material such as analloy of nickel and titanium, commonly referred as nitinol. Theparticular arrangement depicted in FIG. 3, with conductors 92 disposedaround resilient element 94, is not essential. For example, theconductors may be grouped to one side of the elastic element. Probe 72can be placed into the continuous passageway defined by the catheterlumen 30 and bore 28, and can be removed therefrom.

In its free or unconstrained condition, probe body 78 assumes the shapedepicted in FIG. 4. In this shape, hoop region 82 forms a generallycircular hoop 82 in a plane transverse to the axis 96 defined by thedistal-most part of main portion 86. The hoop encircles axis 96 and issubstantially coaxial therewith. The connecting or transition region 84extends outwardly from axis 96 and also slopes slightly in the forwardor distal direction. As discussed below, the probe body, is in thisunconstrained state when deployed within the heart, and accordingly,this condition is also referred to herein as the “deployed” condition ofthe probe body.

In a method according to one aspect of the present invention, theablation device 18 is positioned within a chamber of the heart as, forexample, within the left atrium LA of a subject to be treated. A guidesheath (not shown) is advanced through the venous system into the rightatrium and through the septum separating the right atrium and leftatrium, so that the guide sheath provides access to the left atrium.Typically, the apparatus is advanced through the guide sheath with theballoons in a deflated, collapsed condition. This operation may beperformed by first advancing a guide wire (not shown) into the heart,and then advancing the insertable structure 10, with the balloons in adeflated condition, over the guide wire. During this operation, probe 78is not present in tube bore 28 and lumen 30. The guide wire passesthrough tube bore 28 and through lumen 30. A guide sheath also may beused during the insertion process.

When the ablation device 18 is disposed inside the heart chamber, thephysician manipulates the device using steering mechanism 70 (FIG. 1) tovary the orientation of the ablation device, and hence the orientationof forward-to-rearward axis 26, until the device is positioned in thedesired spatial relationship to the heart, with the axis 26 extendinggenerally normal to the surface of the heart surrounding the ostium OSof a pulmonary vein PV.

As discussed in greater detail in the '757 application, the physicianmay verify the proper disposition of the ablation device relative to theheart by injecting a fluid contrast medium through the continuouspassageway defined by lumen 30 and tube bore 28 and out through port 29on the distal or forward side of the ablation device. Depending upon thepressure with which the contrast medium is injected, some portion of thecontrast medium may pass into the pulmonary vein and other portions mayremain within the left atrium. While the contrast medium is present, thesubject is imaged using an imaging modality which will show the contrastmedium as, for example, conventional x-ray or fluoroscopic imaging.

With the ablation apparatus properly positioned for ablation, thephysician may actuate ultrasonic emitter 23, as by actuating anelectrical energy source (not shown) connected to the emitter 23 byconductors in catheter 30 (also not shown). The ultrasonic emitterdirects ultrasonic energy onto the wall 24 between balloons 20 and 22,where the energy is reflected in a forward direction F and focused intothe ring-like ablation region A. The focused ultrasonic energy heats andablates the myocardial tissue in this region, thereby converting thistissue into scar tissue which is not capable of conducting electricalimpulses.

The physician may detect electrical signals within the pulmonary vein orpulmonary vein ostium by inserting probe 78 into the subject through thecontinuous passageway defined by lumen 30 and tube bore 28. Thephysician manually straightens the hoop region 82 and transition portion84 as these are inserted through the proximal end of the catheter. Theprobe body has sufficient flexibility so that it can be advanceddistally through the passageway. As the probe body advances through thecatheter, the curvature of the probe body conforms to the existingcurvature of the catheter. As the probe body continues to advance, itreaches the condition shown in FIG. 2. In this undeployed condition, thehoop region 82, transition region 84 and main region 86 are disposed inthe continuous passageway, with the distal end 76 of the probe bodyproximal to port 29. As the physician continues to advance the sensorprobe, the distal end 76, hoop region 82 and transition region 84 passdistally out of port 26, whereupon the hoop region and transition regionspring back to their unconstrained or deployed shape, as depicted inFIG. 4. This places the hoop 82 concentric with the axis 96 defined bymain portion 86 of the probe body. However, because the main portion 86is disposed within the tube bore 28 of the ablation device, the mainportion 86 is coaxial with the axis 26 of the ablation device. Thus,hoop 82 tends to deploy in a plane perpendicular to axis 26 of theablation device, with the hoop concentric with the same axis. Asmentioned above, during placement of ablation device 18, the physicianhas already positioned this axis in alignment with the pulmonary veinostium and has positioned this axis generally normal to the plane of theheart tissue encircling the ostium. Thus, the hoop tends to deploy in alocation as shown in FIG. 1, with the hoop lodged within the pulmonaryvein ostium, or (depending upon the diameter of the pulmonary vein) inthe pulmonary vein itself, and with the hoop 82 lying in the planetransverse to the axis of the pulmonary vein and the axis of thepulmonary vein ostium. All of this is accomplished without substantialmanipulation by the physician to aim or locate the hoop. Stated anotherway, the ablation device 18 and catheter 12 act as an introducerstructure which directs the distal portion of the sensor probe intoalignment with the pulmonary vein ostium. Thus, placement of the sensorprobe can be accomplished readily.

Although the catheter and ablation device act to introduce and aim thehoop region of the sensor, the hoop region is not rigidly mounted to theablation device or catheter, and hence, is not rigidly positioned bythese devices. Transition region 84 has some flexibility, so that thehoop 82 can be displaced or tilted somewhat from perfect coaxialalignment with the ablation device. This allows the hoop region toengage the tissues substantially around the pulmonary vein or ostium,even where these anatomical features are not perfectly aligned with theaxis of the ablation device. Also, hoop 82 has some flexibility, andaccordingly can conform to these structures, even where the same are notperfectly circular.

With the hoop 82 engaged with the tissues, electrodes 80 on the hoopwill also be engaged with the tissues and hence will receive electricalsignals propagating within the tissues. The physician can monitor theseelectrical signals using a conventional signal detection system 99connected to connector 88 and hence connected to the electrodes throughthe conductors 92 (FIG. 3) of the sensor probe. If these electricalsignals indicate that abnormal conduction is continuing to occur, thephysician can actuate the ablation device again. The sensing probe neednot be removed from the device during such further ablation.Alternatively, the sensing probe may be removed and other procedures,such as injection of additional contrast medium to confirm the desireddisposition of the ablation device, may be performed. In a furthervariant, the sensor probe may be introduced and placed as describedabove before actuation of the ablation device, most typically aftercorrect placement of the ablation device has been confirmed, as by useof the contrast medium technique discussed above.

In a further variant, the ablation device 18 can be repositioned to anew position as partially depicted in broken lines at 18′ in FIG. 1. Thesensor probe may be retracted into the catheter and ablation device, ormay be entirely removed during the repositioning step. The same steps asdiscussed above may be repeated. The ability to retract or entirelyremove the sensor probe facilitates repositioning. For example, contrastmedium may be injected again to confirm the moved position of theapparatus. Also, because the sensor probe does not project from theapparatus during the repositioning step, it does not interfere withrepositioning.

Apparatus according to a further embodiment of the invention (FIG. 5)includes a catheter 112 and ablation device 118 generally similar to thecorresponding components discussed above with reference to FIG. 1. Hereagain, the ablation device 118 incorporates an expansible balloonstructure incorporating a reflector balloon 120 and a structural balloon122. Here, again, the structural balloon defines a forward or distalsurface 138, and the ablation device incorporates an emitter 123arranged to supply ultrasonic energy which is reflected by the interfacebetween balloons through the front or distal wall 138 of the expandableinflation device into a ring-like focal or ablation region A surroundingthe forward-to-rearward axis 126 of the ablation device. In thisembodiment, the ablation device includes a projection 139 extendingforwardly from forward surface 138, such projection being generally inthe form of a surface of revolution about axis 126. The port 129 at theforward end of the ablation device is disposed on projection 139. In theparticular structure depicted in FIG. 5, projection 139 includes aninflated section of structural balloon 122 and a section at the distalend of the inflated section. A metallic fitting 141 is disposed insideof this section of the balloon, the balloon being cemented to thefitting. The fitting defines port 129. The fitting may cooperate with aspring (not shown) and with the reinforcing elements to provide thespring-back collapsing and twisting action as discussed above duringcollapse of the balloon, and to provide the reinforcement againstdisplacement transverse to the axis, as discussed above. Here again,catheter 112 and ablation device 118 cooperatively define a continuouspassageway, including a lumen 130 of catheter 112 and the bore 128extending through the ablation device to port 129.

The apparatus includes a sensor probe 172 which can be inserted into orremoved from the continuous passageway. The probe incorporates aself-deploying probe body 178 depicted in its deployed condition inFIGS. 5 and 6. The probe body includes a base or main portion 186 and ahoop region 182 which, in the deployed condition, forms a substantiallyclosed, circular hoop. The probe body also includes a limb portion 184extending from the distal end of the main portion to the hoop region. Asin the embodiments discussed above, the probe 172 has electrodes 180disposed on the hoop region. The probe body 178 also includes leads, adielectric and a resilient structure which may be similar to thosediscussed above, the leads serving to connect the electrodes 180 with aconnector (not shown) at or adjacent the proximal end of the probe.

In the embodiment of FIGS. 5 and 6, the limb portion 184 extendsoutwardly from the main portion and also extends rearwardly orproximally from the distal end of the main portion, so that the hoopregion 182 is disposed to the rear of the distal end 187 of the mainportion. In the deployed condition, hoop region 182 encircles the baseor main portion 186. When the probe is in its deployed condition andcompletely unconstrained, hoop region 182 lies generally in a planetransverse to the axis of main or base portion 186, but has a slightcurvature in the distal direction, i.e., towards the distal end of themain portion 186. Stated another way, the tip 183 of the hoop regionfurthest from limb portion 184, as measured by distance traveled alongthe length of the hoop region, lies closer to the distal end 187 thanthe juncture 185 of the hoop region and limb portion. The hoop region isquite flexible in the axial direction, so that tip 183 can be displacedaxially and the hoop region may be flattened into a planar structurewith only minimal force applied to tip 183 in the axial direction.

As in the embodiments above, the probe body is advanced by straighteningit and sliding it through the continuous passageway defined by the lumen130 of the catheter and the bore 128 of the ablation device. Here again,in an undeployed condition, the hoop region 182, limb 184 and base ormain portion 186 are disposed within the passageway and hence conform tothe curvature of the passageway. In the deployed condition (FIG. 5), thehoop region 182 encircles the axis 126 of the ablation device andencircles projection 139. The base portion 186 of the probe body isaligned with axis 126 and projects through port 129, whereas limbportion 184 extends radially outwardly from axis 126 and also extendsrearwardly or proximally to the hoop region. Placement of the hoopregion around projection 139 allows hoop region 182 to abut the forwardsurface 138 of the ablation device and allows the physician to urge theablation device forwardly or distally so as to bring the hoop regioninto firm engagement with the tissues. This arrangement is particularlyuseful where the hoop region has a diameter larger than the diameter ofthe pulmonary vein, so that the hoop region is to be engaged with aportion of the heart wall which extends generally transverse to axis126. For example, where ablation region A is of a diameter selected toablated tissue surrounding the ostium, it may be desirable to engagehoop region 182 and electrode 180 with a part of the heart wallsurrounding the ostium, rather than with tissue inside the ostium or inthe pulmonary vein. The hoop region may be of larger diameter or smallerdiameter than the ablation region A.

The sequence of operations used to deploy the sensor probe of FIGS. 5and 6 is depicted schematically in FIGS. 7-14. In these figures, theintroducing structure, including the catheter and ablation device shownin FIG. 5 are symbolized by a generalized body 101. Also, thedescription uses a coordinate system with mutually orthogonal X, Y and Zdirections. This coordinate system is associated with the main portion186 of the probe body. Rotation of the main portion of the probe bodyabout its own axis and about the axis 126 defined by the ablation devicehas no effect on the operations discussed with reference to FIGS. 7-13.As the probe body is advanced out through port 129, the leading end ofthe probe body is that portion which will ultimately form the tip 183 ofthe hoop region discussed above with reference to FIG. 6. This leadingportion has a natural or unconstrained curvature relative to thenext-trailing portion in a first or −X radial direction, in the X-Zplane, and thus deflects toward the −X axis when the probe is firstadvanced out through the port 129, as depicted in FIG. 7. The next partof the probe, hoop region 182 has a free or unconstrained curvature inthe Y-Z plane, orthogonal to the curvature of portion 183. Thus, as hoopregion 182 is progressively advanced out of port 129 (FIGS. 8 and 9), itcurves relative to structure 101 and relative to the trailing portionsof the probe body in the Y-Z plane, and thus first swings the leadingtip portion in the +−Y direction, away from axis 126 and introducerstructure 101, so that the tip portion moves generally in the +−Ydirection. However, as more of portion 182 is advanced out of the port,the curvature of the hoop region causes the tip portion 183 to movegenerally in the opposite, −Y direction (FIG. 10), back towards axis 126and introducer structure 101, until the tip portion 183 engages theintroducer structure 101.

Because the tip portion 183 is curved in the −X direction, it provides a“lead-in” so that as tip 183 is urged further in the −Y direction by thedeploying hoop region 182, tip portion 183 will tend to slide on theintroducer structure 101 in the −X direction. Thus, as the hoop region182 is further deployed, it will reliably pass on the −X side ofintroducer structure 101 and axis 126, so that the structure reaches thecondition depicted in FIG. 11, with the juncture 185 of the hoop regionand limb portion emerging from port 129. In this condition, hoop region182 has formed a ring or hoop, with a portion of the hoop opposite fromjuncture 185 and tip portion 183 disposed on the −X side of theintroducer structure 101.

As the limb portion 184 emerges from port 129, the loop travels in the+Z direction (FIG. 12) until the juncture between limb portion 184 andbase portion 186, at the distal end 187 of the base portion, begins toemerge from the port. The curvature of the juncture at the distal end187 of the base portion swings the limb portion in an arc in the Y-Zplane, so that the juncture 185 of the limb portion and hoop region 182first moves in the +X direction and in the −Z or rearward direction. Asthe juncture 187 at the distal end of base portion 186 continues toemerge from the port, continued movement swings juncture 185 and hoop182 in the −X direction, as well as in the −Z or rearward direction, asseen in FIG. 14. This action brings the hoop region 182 to the fullydeployed condition depicted in FIGS. 5 and 6. During this final phase ofdeployment, portion 182 may or may not bear on a forwardly ordistally-facing wall 105 of the introducer structure as, for example,wall 138 of the expandable ablation device seen in FIG. 5.

During deployment of the sensor probe discussed with reference to FIGS.5-14, the expansible inflation device 118 may be temporarily retractedin the proximal or rearward direction relative to the wall of the heart,so as to provide clearance for movement of the hoop forward of thestructure, as seen in FIGS. 12 and 13.

Numerous variations and combinations of the features discussed above canbe utilized without departing from the present invention. Merely by wayof example, it is not essential that the ablation device include theultrasonic element and reflectors discussed above. For example, anexpandable balloon having electrodes suitable for ablation orarrangements for delivering optical energy may be used. Also, the probeand method of probe deployment discussed above with reference to FIGS.5-13 may be used for purposes other than sensing electrical signals inthe context of an ablation process. For example, the probe can be usedin a cardiac mapping operation, distinct from an ablation process. In afurther variant, the functional elements of the probe (the sensingelectrodes 180) may be used as ablation electrodes; or may be replacedby functional elements other than electrodes as, for example, discreteultrasonic transducers or the like for an ablation process; or bysensors other than electrodes as, for example, chemical sensors.Further, although the present invention is particularly useful inperforming procedures within the heart, it can be applied to performingprocedures within other internal organs of a human or animal subject, orindeed, to performing procedures within a cavity of an inanimatesubject.

A sensor probe in accordance with a further embodiment of the inventionhas a composite body 200 (FIG. 15) including a tubular metallic shaftsection 202 which may be formed from a stainless steel tube of the typecommonly used to form hypodermic needles. The shaft section definesinterior bore 203 (FIG. 16). Desirably, the shaft section has an outsidediameter D_(s) (FIG. 16) on the order of 1.25 mm or less, more desirablyabout 1 mm (0.040 inches) or less, and most preferably about 0.9 mm(0.035 inches). Preferably, the shaft section 202 extends throughout themajority of the length of the probe 200. For example, the shaft sectionmay be on the order of 140 cm (55 inches) long.

A distal section 206 is mounted to the distal end 204 of shaft section202. The distal section 206 includes a wire core 210 (FIG. 17) with adielectric, biologically inert polymeric covering 212 overlying thecore. The core desirably is formed from a metal such as anickel-titanium alloy which can be formed to a preselected shape andwhich will tend to return to the preselected shape when unconstrained. Aplurality of electrodes 216 overlie the covering 212 in a portion of thelength of the distal section. As best seen in FIGS. 15 and 18, thisportion 208 of the distal section in its free or unconstrained conditionforms a hoop lying in a plane transverse to the axis defined by theremainder of the distal section. In the free or unconstrained condition,the distal section may extend about 5 cm (2 inches) proximally from theplane of the hoop. The distal section 206 is formed to this hoop shapeand tends to return to this shape when the distal section isunconstrained. However, the distal section is quite flexible, and hence,can be constrained to a straight or gently curving shape, so as to beadvanced through the passageway defined by the catheter and ablationdevice as discussed above. Shaft section 202 is flexible enough to passthrough gently curving portions of the catheter, but is considerablystiffer than the distal section.

The proximal end of the distal section 206 abuts the distal end 204 ofthe shaft section and is bonded to the shaft section 202. Desirably,wire core 210 extends into the bore 203 of the shaft section a shortdistance from this abut joint. A plurality of fine insulated wires 220are disposed within the bore 203 of the shaft section. These wires areelectrically connected to electrodes 216 on the distal section. Theprobe body also includes a proximal section 222 and a transition section224 extending from the proximal section to the proximal end 226 of theshaft portion. The proximal end section may include a relatively stiffpolymeric tube having an interior bore (not shown). The transitionsection 224 may include a polymeric tube having stiffness intermediatebetween that of the proximal end section and the shaft section, thistube also having an interior bore. The interior bores of the transitionsection 224 and proximal section 222 may communicate with the bore ofshaft section 202. Alternatively, the metallic tube forming shaftsection 202 may extend through the interior bores of the transitionsection and the proximal section. In either arrangement, wires 220 mayextend all the way to the proximal end of proximal end section 222. Anelectrical connector 230 is connected to these wires and, hence, toelectrodes 216.

In use, the probe body according to this embodiment, can be advanced anddeployed as discussed above. The shaft portion 202 constituting themajor portion of the probe length has a appreciable stiffness. Moreover,the shaft portion is smooth and slides readily within the structuresdefining the passageway. Therefore, the probe does not tend to buckleand jam as the probe is threaded through the passageway of the catheter.During threading, of course, the distal end portion is not in thehoop-shape shown, but instead is straight or slightly curved to matchthe curvature of the passageway in the catheter. Typically, the distalend portion 206 is substantially more flexible than the shaft portion202. The joint between the distal end portion and the shaft portion (atthe distal end 204 of the shaft portion) most preferably lies justproximal to the bendable section 62 of the catheter when the probe isfully advanced.

As these and other variants can be employed, the foregoing descriptionof the preferred embodiments should be taken by way of illustrationrather than by way of limitation of the invention as further set forthin the claims.

INDUSTRIAL APPLICABILITY

The present invention can be utilized in medical and veterinarytreatment.

1. Apparatus for cardiac treatment comprising: (a) a catheter havingproximal and distal ends; (b) an expansible ablation device includingone or more balloons mounted to said catheter at or adjacent the distalend thereof, said ablation device having a collapsed condition and anexpanded condition, said balloon ablation device being operative toablate cardiac tissue in proximity to the ablation device when theablation device is in said expanded condition, said catheter and saidablation device in said expanded condition defining a port open on thedistal side of said one or more balloons and a continuous passagewayextending between said port and the proximal end of the catheter, saidcatheter being steerable so that the orientation of said expandableablation device relative to the heart can be selectively varied; and (c)an elongated sensor probe having proximal and distal ends, a mainportion, an open hoop region, and a limb portion coupling the mainportion to the hoop region, wherein the limb portion extends radiallyaway from the main portion and extends proximally from a distal end ofthe main portion, said sensor probe including one or more electrodesdisposed adjacent the distal end of the sensor probe, said passagewayand said ablation device being constructed and arranged so that saidsensor probe can be removably positioned in said passageway with thedistal end of said sensor probe projecting out of said ablation devicethrough said port, wherein the distal end of the sensor probe has anunconstrained curvature relative to the hoop region, and the hoop regionhas an unconstrained curvature in a plane orthogonal to the curvature ofthe distal end, resulting in an unconstrained configuration in which thehoop region is curved in the distal direction, towards the distal end ofthe main portion, and the distal end of the sensor probe is angled suchthat it lies closer to the distal end of the main portion than ajuncture between the hoop region and the limb portion.
 2. Apparatus asclaimed in claim 1 wherein said expansible ablation device isconstructed and arranged to direct energy into a loop-like regionencircling said port.
 3. Apparatus as claimed in claim 2 wherein saidexpansible ablation device includes an ultrasonic emitter and said oneor more balloons form an expansible energy-directing structure adaptedto direct ultrasonic energy from said emitter into said loop-like regionwhen said expansible ablation device is in said expanded condition. 4.Apparatus as claimed in claim 3 wherein said one or more balloonsinclude a structural balloon and a reflector balloon defining a commonwall so that when said expandable structure is in said expandedcondition with said structural balloon inflated with a liquid and saidreflector balloon inflated with a gas, said balloons form an interfacereflective to ultrasonic energy at said common wall.
 5. Apparatus asclaimed in claim 3 wherein said expansible ablation device defines aforward-to-rearward axis, said loop-like region having an axissubstantially coaxial with said forward-to-rearward axis of saidablation device, said energy-directing structure being arranged todirect said ultrasonic energy into said region in a direction having aforward component.
 6. Apparatus as claimed in claim 3 wherein said portis disposed on said forward-to-rearward axis and wherein the hoop regionof said sensor probe carries said one or more electrodes, said sensorprobe being constructed and arranged so that said hoop region tends toform a hoop coaxial with said forward-to-rearward axis and saidloop-like region when said hoop region projects from said port. 7.Apparatus as claimed in claim 2 wherein one of said balloons of saidexpansible ablation device includes a distal wall, said loop-like regionoverlying said distal wall in said expanded condition, said port beingdisposed on said distal wall.
 8. Apparatus as claimed in claim 7 whereinthe hoop region of said sensor probe carries said one or moreelectrodes, said sensor probe being constructed and arranged so thatsaid hoop region tends to form a hoop when said hoop region projectsfrom said port.
 9. Apparatus as claimed in claim 8 wherein said hoop issubstantially coaxial with said loop-like region.
 10. Apparatus asclaimed in claim 8 wherein said hoop is disposed distal to said port.11. Apparatus as claimed in claim 8 wherein said hoop overlies saiddistal wall.
 12. Apparatus as claimed in claim 11 wherein said distalwall includes a main portion and a tip portion projecting distally fromsaid main portion, said port being disposed on said tip portion, saidhoop overlying said main portion so that said hoop is disposed proximalto said port.
 13. Apparatus as claimed in claim 1 wherein said catheterincludes a bendable section adjacent the distal end of the catheter butproximal to the ablation device.
 14. Apparatus as claimed in claim 13further comprising one or more pull wires, each said pull wire having adistal end connected to the catheter distal to said bendable section orto said ablation device, said one or more pull wires being slidablymounted to the catheter so that the bendable section can be selectivelybent by pulling one or more of said pull wires.
 15. Apparatus as claimedin claim 1 wherein said sensor probe includes a tubular metallic shaftsection and a distal section connected to the distal end of said shaftsection, said distal section including the hoop region carrying the oneor more electrodes, said sensor probe further including one or moreconductors electrically connected to said one or more electrodes,portions of said conductors extending within said shaft section. 16.Apparatus as claimed in claim 15 wherein said distal end sectionincludes a wire core, a polymeric covering overlying said wire core,said one or more electrodes overlying said polymeric covering so thatsaid covering insulates at least some of said electrodes from said core.17. A sensor probe comprising: (a) an elongated tubular metallic shaftsection having proximal and distal ends; (b) a elongated distal sectionhaving proximal and distal ends including a metallic wire core and apolymeric covering overlying said wire core, one or more electrodesoverlying said polymeric covering, said distal section having anunconstrained shape including a main portion, a hoop region, and a limbportion coupling the main portion to the hoop region, wherein the limbportion extends radially away from the main portion and extendsproximally from a distal end of the main portion, said hoop regionhaving said one or more electrodes thereon, wherein the distal sectionin the unconstrained shape includes an opening in the hoop region, andthe hoop region has a curvature in the distal direction and the distalend of the distal section is angled such that it lies closer to thedistal end of the main portion than a juncture between the hoop regionand the limb portion; and (c) one or more electrical conductorsextending within said shaft section, said electrical conductors beingelectrically connected to said electrodes.
 18. A probe as claimed inclaim 17 wherein said shaft section and said distal sections havecross-sectional dimensions of about 1.25 mm or less.
 19. A probe asclaimed in claim 18 wherein said one or more electrodes include aplurality of electrodes.
 20. A probe as claimed in claim 17 wherein saiddistal section is substantially more flexible than said shaft section.21. A method of cardiac ablation comprising the steps of: (a) advancingan apparatus including a catheter and an expansible ablation deviceincorporating one or more balloons into a subject while said ablationdevice is in a collapsed condition until the ablation device is disposedin a chamber of the subject's heart; (b) expanding the ablation deviceto an expanded condition by inflating said one or more balloons; (c)while said ablation device is in said expanded condition, positioningthe ablation device in a desired disposition relative to the heart byselectively steering said catheter so as to bring the ablation structureto a desired orientation relative to the heart; (d) actuating theablation device to apply energy in a loop-like region in a predeterminedspatial relationship to said ablation device and thereby ablate tissuein said region to form a lesion; (e) while said ablation device is insaid expanded condition, retracting the ablation device in the proximaldirection, and advancing a sensing probe through a passageway in saidcatheter and said ablation device so that a distal tip of said sensingprobe projects out of a port on said ablation device, said sensing probefurther including a main portion, a hoop region, and a limb portioncoupling the main portion to the hoop region, wherein the limb portionextends radially from the main portion and extends proximally from adistal end of the main portion; (f) advancing the sensing probe out ofthe port, wherein the tip has an unconstrained curvature relative to thehoop region in a first radial direction, and the hoop region has anunconstrained curvature in a plane orthogonal to the curvature of thetip, such that as the hoop region is advanced out of the port, the hoopregion forms a ring or hoop shape and the tip and hoop region aredisposed on the same side of the ablation device, wherein as the limbportion is advanced through the port, the hoop region swings down overthe distal end of the main portion and encircles the main portionproximal of the distal end of the main portion; (g) advancing theablation device distally until the hoop region of the sensing probeabuts the ablation device, and further advancing the ablation deviceuntil the hoop region contacts tissue of the subject adjacent saidablation device and said ablation device at least partially positionsthe hoop region relative to the heart; and (h) detecting electricalsignals in the subject using said sensing probe.
 22. The method asclaimed in claim 21 wherein said steps of advancing the sensing probeand detecting electrical signals are performed after said step ofactuating said ablation device.
 23. The method as claimed in claim 21wherein said steps of advancing the sensing probe and detectingelectrical signals are performed a first time before said step ofactuating said ablation device.
 24. The method as claimed in claim 23further comprising the step of repeating said detecting step after saidstep of actuating said ablation device.
 25. The method as claimed inclaim 24 further comprising the step of withdrawing said sensing probeafter detecting electrical signals the first time and reinserting saidsensing probe prior to repeating said detecting step.
 26. The method asclaimed in claim 21 further comprising the step of injecting a contrastmedium through said passageway while said sensing probe is not disposedtherein.
 27. The method as claimed in claim 21 wherein said port issubstantially coaxial with said loop-like region and step of advancingsaid sensing probe is performed so that said hoop region is within saidloop-like region.
 28. The method as claimed in claim 27 wherein saidstep of positioning said ablation device is performed so that saidloop-like region at least partially surrounds the ostium of a pulmonaryvein and said port is aligned with such ostium.
 29. The method asclaimed in claim 28 wherein said step of advancing said sensing probe isperformed so that said hoop region is disposed within the ostium or thepulmonary vein.
 30. The method as claimed in claim 27 wherein said stepof advancing said sensing probe is performed so that said each portionof said sensing region moves out through said port in a forwarddirection and so that when the sensing probe is fully advanced, the limbportion extends rearwardly so that the hoop region lies in proximity tothe ablation device.
 31. A probe including a probe body having anundeployed condition and a deployed condition, and one or morefunctional elements disposed along said probe body, said probe bodybeing elongated and flexible in said undeployed condition, said probebody in said deployed condition including: (a) a base portion extendingin a distal direction to a distal end; (b) a limb extending from thedistal end of said base portion in a radial direction transverse to saiddistal direction, said limb also extending in a proximal directionopposite to said distal direction, said limb having an outer end remotefrom said base portion; (c) an open hoop region extending from saidouter end of said limb around said base portion to a tip, said hoopincluding one or more of said functional elements, wherein the tip hasan unconstrained curvature relative to the remainder of the hoop region,wherein the probe is configured such that when in an unconstrained,deployed condition, the hoop region has a curvature in the distaldirection, towards the distal end of the base portion, and the tip ofthe hoop region is angled such that it lies closer to the distal end ofthe base portion than a juncture between the hoop region and the limb.32. The probe as claimed in claim 31, further comprising an introducerstructure having proximal and distal ends, a port adjacent the distalend of the introducer and a passageway extending from adjacent saidproximal end to said port, said probe body in said undeployed conditionbeing slideable in said passageway, said base portion of said probe bodyin said deployed condition projecting from said port.
 33. The probe asclaimed in claim 32 wherein said hoop region of said probe body extendsaround said introducer structure when said probe body is in saiddeployed condition.
 34. The probe as claimed in claim 32 wherein saidintroducer structure includes a catheter having proximal and distal endsand an expansible ablation device mounted to the distal end of saidcatheter, said ablation device having a collapsed condition and anexpanded condition, said ablation device being operative to apply energyto tissue in proximity to the ablation device when the ablation deviceis in said expanded condition.
 35. The probe as claimed in claim 34wherein said ablation device is adapted to apply energy in a loop-likeregion surrounding said port.
 36. The probe as claimed in claim 35wherein said ablation device includes an ultrasonic emitter and anexpansible energy-directing structure adapted to direct ultrasonicenergy from said emitter into said loop-like region when said expansibleablation device is in said expanded condition.
 37. The probe as claimedin claim 36 wherein said expansible ablation device defines aforward-to-rearward axis, said loop-like region having an axissubstantially coaxial with said forward-to-rearward axis of saidablation device, said energy-directing structure being arranged todirect said ultrasonic energy into said region in a direction having aforward component.
 38. The probe as claimed in claim 37 wherein saidport is disposed adjacent to said forward-to-rearward axis, said baseportion of said probe body extends substantially parallel to saidforward-to-rearward axis of said ablation device and said hoop region ofsaid probe body extends around said forward-to-rearward axis when saidenergy-directing structure is in said expanded condition and said probeis in said deployed condition.
 39. The probe as claimed in claim 38wherein said energy-directing structure in said expanded conditionincludes a distal wall, said loop-like region overlying said distalwall, said hoop region of said probe body overlying said distal wallwhen said energy-directing structure is in said expanded condition andsaid probe is in said deployed condition.
 40. The probe as claimed inclaim 39 wherein said energy-directing structure includes a projectionextending forwardly from said distal wall when said energy-directingstructure is in said expanded condition, said axis extending throughsaid projection, said port being disposed on said projection, said hoopregion of said probe body encircling said projection when said probe isin said deployed condition.
 41. The probe as claimed in claim 39 whereinsaid port extends through said distal wall.
 42. The probe as claimed inclaim 32 wherein said probe is removably received in said passageway.43. The probe as claimed in claim 32 wherein said probe body isresilient and a portion of the probe body projecting out of said port isadapted to deform under its own resilience to form said limb and saidhoop region when said probe body is advanced distally relative to saidintroducer structure.